FRICTION OF ULTRA-HIGH-MOLECULAR-WEIGHT POLYETHYLENE, MODIFIED WITH CARBON NANOTUBES

The present study investigates the coefficient of friction of new composites based on UHMWPE with the addition of different percentages of carbon nanotubes (CNTs) - 0.5%, 0.75%, 1.0% and 1.5%. UHMWPE samples with carbon nanotubes, samples of 0.5%, 0.75%, 1.0% and 1.5% carbon nanotubes (UHMWPE-CNTs) and samples with the same carbon nanotube content were made, but with carbon nanotubes subjected to Electroless Nickel Composite Coating with nanoparticles of SiC (UHMWPE-NiCNTs). The coefficient of friction is investigated with a tribometer in a kinematic scheme "Thumb-Disc" without lubricant in a high-alloy steel frame with hardness HRC=56.9 and roughness Ra=2.35 μm. All samples were tested under the same friction conditions - friction path, sliding speed, roughness of the counterpart and samples, ambient temperature. Results and regularities of the effect of carbon nanotubes UHMWPE-CNTs and UHMWPE-NiCNTs on the coefficient of friction at different normal loads are obtained. The microhardness of the materials under investigation was measured and its relationship to the percentage of CNTs and NiCNTs and to the coefficient of friction was analyzed. It was found that the highest micro-hardness belongs to the materials with 1.5% carbon nanotubes having a composite nickel plating (UHMWPE- 1.5NiCNT). This study and the results are related to the implementation on contract: ДН 07/28-15.12.2016 "Research and creation of new wear-resistant coatings using composites and nanomaterials", funded by the National Science Fund at the Ministry of Education and Science, Bulgaria.